The present invention relates generally to storage systems and, more particularly, to tiered storage pool management and control for loose coupled multiple heterogeneous storage environment. The loosely coupled connection uses standardized network and not-wide (narrower than internal bus) network, and control of each device connected to the network is independent from that of other devices. By using the loosely coupled connection, one can consolidate heterogeneous (multi-vender, multi-type of product, and multi-generation of product) devices to one system.
Storage virtualization is a technology that is widely used. Examples include thin provisioning and page-based tiered storage. The use of storage virtualization technology can improve storage usability and efficiency. The improvement of usability is by concealment of the internal configuration (e.g., disk configuration, tier configuration, data location and so on). The improvement of efficiency is by sharing of the storage resources (e.g., disk workload, processor workload, internal bus workload, capacity and so on). Generally speaking, these storage virtualization techniques can be applied only in one storage controller. One exception is the case involving the “Mount of external volume” function, wherein the external volume mount function is suitable for the tiered management situation between a high performance storage subsystem and a low cost storage subsystem. However, it will cause a waste of resource and unnecessary overhead for performance by connecting a high performance storage subsystem to a high performance storage subsystem. Many users have a plurality of storage subsystems in their IT (Information Technology) system. Each storage subsystem is independent from the other storage subsystems. This causes difficult and troublesome storage system management for the system design and system operation. The result is a waste of resources in the overall storage system due to the difficulty of resource sharing between two high performance storages. It is difficult to manage the total resource amount and improve the efficiency in the environment involving multiple storage subsystems.